Associate Professor Department of Geology and Mining, University of Rajshahi, Rajshahi 6205, Bangladesh Phone: (+88) 0721-711111 (W), (+88) 0721 750974 (Res.), Mobile:(+88) 01741-243440, Fax: (+88) 0721-750064.
Abstract: Eleven facies (St, Sp, Sh, Sr, Sw, Sl, Sf, Fsl, Fl, Fm, and Fb) have been identified in a section of the Boka Bil Formation of Bangladesh. These facies have been grouped into three facies associations; (i) sandstone facies association of tidal channel and estuarine environments (SFTE), (ii) heterolithic facies association of tidal flat environments (HFTF) and (iii) shale facies association of deep-sea environments (SFDS). The SFTE includes facies St, Sp, Sh and/or Sr, whereas HFTF contains facies Sr, Sw, Sl, Sf, Fsl and Fm. The SFDS includes facies Fb only. The SFTE association indicates deposition under tidal action in tidal channels and estuarine tidal creeks where maximum water depth was about 7 m. Paleocurrents from the facies St, Sp and Sr show strong bi-directional, bi-polar of tidal action. Facies association HFTF suggests a mixed and mud-dominated tidal flat, where maximum water depth was about 33 cm. The association of SFDS with laminated greenish gray to black shale facies containing both calcareous and non-calcareous embodied ripple laminated siltstone (Tc division) and parallel laminated siltstone (Td division), indicate deposition both above and below the CCD in deep marine environments. Overall, the Boka Bil Formation was deposited in tidal flat, tidal channel and estuarine to deep marine environments.
